A wide range of transporters and methods are known for transporting human subjects. Typically, such transporters rely upon static stability and are designed for stability under all foreseen conditions of placement of their ground-contacting members with an underlying surface. For example, a gravity vector acting on the center of gravity of an automobile passes between the points of ground contact of the automobile's wheels and the suspension of the automobile keeps all wheels on the ground at all times making the automobile stable. Although, there are conditions (e.g., increase in speed and sharp turns) which cause otherwise stable transporters to become unstable.
A dynamically stabilized transporter, also known as a balancing transporter, is a type of transporter that has a control system that actively maintains the stability of the transporter while the transporter is operating. The control system maintains the stability of the transporter by continuously sensing the orientation of the transporter, determining the corrective action necessary to maintain stability, and commanding the wheel motors to make the corrective action. If the transporter loses the ability to maintain stability, such as through the failure of a component or a lack of sufficient power, the rider may experience a sudden loss of balance.
For vehicles that maintain a stable footprint, coupling between steering control and control of the forward motion of the vehicles is not an issue of concern. Under typical road conditions, stability is maintained by virtue of the wheels being in contact with the ground throughout the course of a turn. In a balancing transporter, however, any torque applied to one or more wheels affects the stability of the transporter. Coupling between steering and balancing control mechanisms is one subject of U.S. Pat. No. 6,789,640, which is incorporated herein by reference.